With a transformerless output (it uses a second vacuum tube instead), the Gemini II has a sparkle and sheen to its sound that works particularly well for picked and strummed acoustic guitars.
The 4400a is a FET mic with a transformer on its output, and the highs aren't quite as forward as with the Gemini - but it's got a fullness and body that provide a great sense of depth to each note.
Hear the difference below! What do you think?
Both mics were positioned approximately 14" from the base of the guitar's neck. They were recorded through a pair of Rupert Neve Designs Shelford 5052s with no EQ, compression, or other processing applied.